Measurement caliber for municipal drainage pipes and rainwater-inlet connectors: by design centerline length without deducting manholes and inlets (Beijing/national), versus regional manhole-deducting calibers

Topic Positioning

This card answers a high-frequency municipal takeoff dispute: is pipe/connector length measured to manhole (inlet) centers or inner faces, and are manhole lengths deducted ("where does deduction start")? It gives the current Beijing and national calibers, regional differences, and practice points.

Core Conclusions

1. Beijing (DB11/T 2382-2024) — centerline, no manhole deduction

• Clause 7.4.26 (drainage pipe laying): "Drainage pipe laying is preferably set by reinforced-concrete, concrete, and plastic pipes with different joints; consumptions preferably include water-tightness testing; quantities are computed by design centerline length, without deducting auxiliary structures; pipes laid in sleeves: labor x 1.10."
• Clause 7.4.31: "Rainwater-inlet connectors follow Clause 7.2.15."
• Clause 7.2.15 (road works): "Connector laying quantities are computed by design centerline length." -> Measure straight through along drawing centerlines; no deduction for manholes or inlets; no center-vs-edge operation exists.

2. National BOQ (GB/T 50857-2024) — same as Beijing

• Appendix E, Table E.1.1 "pipe laying" (040501): by design centerline length, no deduction of auxiliary structures, fittings, valves; BOQ and quota both "centerline, no deduction" — no conversion needed.
• Appendix E, Clause E.5.6: "rainwater-inlet connectors are listed per the pipe-laying items of Appendix E.1."

3. Regional difference (the true source of the "datum" dispute)

• Shenzhen SJG 181.4-2024 Vol. 4, Clause 1.2.3: "Drainage pipe laying quantities are computed in meters as the center-to-center length minus manhole lengths; per-manhole deductions per Table 1.2.3." Measure center-to-center first, then deduct per manhole per the table.
• Under the Beijing caliber, do not apply manhole deduction; cross-region projects must confirm the applied volume's rules first.

4. Workmanship != measurement (often misused)

• DB11/T 1493-2017 Clause 6.1.3: "One connector end flush with the inlet inner wall, the other protruding not more than 20 mm into the manhole." That is a masonry/installation requirement (where pipe ends actually reach), not a basis to compute "face-to-face net length"; measurement remains by design centerline.

5. Listing reference (Beijing)

• Connectors in m under Table D.2.14: D2-3-50 (D300), D2-3-51 (D400), work content: pipe setting, concrete placing, curing, etc.;
• Standard manholes by design count per unit (Clauses 7.4.25/7.4.32);
• Pipes (m) and manholes (units) measured independently, no mutual deduction.

Applicable Boundaries

• "Centerline, no manhole deduction" applies under DB11/T 2382-2024 or GB/T 50857-2024; regions with manhole-deduction calibers (e.g., SJG 181.4-2024) follow their own standards — do not transplant this card's Beijing caliber.
• Technical end-position requirements constrain installation only, not deduction or run conversion.
• Boundaries between network and general-installation piping (e.g., water/sewer at municipal connection points, meter pits, valve pits) per DB11/T 2382-2024 Clause 7.4.1 — a listing-boundary matter not changing the centerline measurement.
• This card covers measurement calibers only, not rates or fees.

Further Reading

• DB11/T 2382-2024 Section 7.4 networks (7.4.1 boundaries, 7.4.25/7.4.32 standard manholes, 7.4.26 drainage laying, 7.4.31 connectors), Section 7.2 roads 7.2.15; Appendix D Table D.2.14 connectors (D2-3-50, D2-3-51).
• GB/T 50857-2024 Appendix E: E.1 pipe laying (Table E.1.1, 040501), E.5.6.
• SJG 181.4-2024 Vol. 4, Clause 1.2.3 and Table 1.2.3 "per-manhole deduction lengths".
• DB11/T 1493-2017 Clause 6.1.3.